I’ve been using this Roof Top Cargo Bag for the past 6 years. It stores a ridiculous amount of gear, it’s extremely durable (the material is rubber laminated nylon) and it’s waterproof. There are 8 straps that attach to your cars Roof Rack, which keeps it in place for the whole trip up to your campsite.

I-Want-That-For-Camping-Roof-Top-Cargo-Bag